箔片结构库伦摩擦效应对径向箔片轴承特性的影响

基于有限元法建立波箔型气体径向轴承箔片结构的库伦摩擦模型,通过改变平箔片与波纹箔片之间以及波纹箔片与轴承座之间的摩擦因数,对比分析了在各种载荷分布条件下波纹箔片库伦摩擦模型与文献中线性弹簧模型的刚度特性,研究了库伦摩擦效应对波纹箔片刚度特性的影响规律.在此基础上,运用有限单元法和有限差分法求解雷诺方程和气膜厚度方程,研究了在两个工作转速下气体波箔片轴承中截面处最小气膜厚度随轴承承载力的变化规律以及承载力随偏心率的变化规律.通过数值仿真对该模型、文献中线性弹簧模型和刚性表面气体轴承进行对比分析,并把气膜厚度分布与文献结果进行了对比.结果表明:箔片的库伦摩擦力在一定程度上增大了波纹箔片的刚度,并且随着摩擦因数的增大其刚度以及两端固定的波纹箔片个数也增加,使得箔片轴承表面变“刚”,因此轴承静特性更趋于刚性表面轴承,此外当轴承承载力一定时,箔片摩擦因数越大轴承的最小气膜厚度越小.

Effects of Coulomb friction in foil structure on foil journal bearing performance

The Coulomb friction model of foil structure of bump foil journal bearing was developed by using finite element mothod.Through changing friction coefficients between top foil and bump foil,bump foil and bearing housing,the stiffness of foil strucure of Coulomb friction model and linear spring model from literatures were compared under various load distributions,and the effects of Coulomb friction on stiffness of bump foil were studied.Then,by using finite element mothod and finite difference method,the compressible gas lubricated Reynolds equation and the film thickness equation were solved together.Predictions of the minimum gas film thickness on bearing mid-plane for increasing static loads and load capacity versus eccentricity ratio at two speeds were obtained.The numerical results of this finite element model were compared with those of linear spring model and rigid surface gas bearing,and the predicted film thickness was also compared with test data.The results indicate that Coulomb friction force can enhance the stiffness of bump foil.With the increase of friction coefficient,the stiffness of bump foil and number of bump foil with both ends fixed are also increased,so the surface of foil bearing is made to be hard,and static performance of bearing is similar to that of rigid bearing.Moreover,when the bearing load capacity is fixed, the minimum film thickness decreases with the increase of foil friction coefficient.